Post by Infinity Blade on Jun 16, 2021 20:35:24 GMT 5
Golden eagle predation on cranes. This study looked at golden eagles preying on captive-reared cranes, but here's some information on what appears to be predation on wild individuals (Ellis et al., 1999).
And some interesting notes on cooperative hunting.
However, there are only six published observations of Golden Eagles taking adult-sized cranes in North America. Two extensive reviews of Golden Eagle prey did not report cranes at all (Olendorff 1976, Sherrod 1978). Recently, three wild adult Greater Sandhill Cranes (Grus canadensis tabida; GSHC) were reported as prey (details lacking) at Malheur National Wildlife Refuge, Oregon (Littlefield and Lindstedt 1992), and a single juvenile Whooping Crane (G. americana; WC) was killed by a Golden Eagle on its first southward migration in company with its GSHC foster parents (Windingstad et al. 1981). Johns (1977) reported an eagle attack on an adult SHC in Saskatchewan in October. Golden Eagle predation on captive-reared GSHCs (released as iuveniles and yearlings at Grays Lake, Idaho) is belikved to have caused the failure of that effort (Bizeau et al. 1987: R. C. Drewien, pers. comm.). Surprisingly, crane chicks have been reported as prey of Golden Eagles only once in North America (Ivey and Scheuering 1997). In preparing this manuscript, we learned of two unpublished instances of Golden Eagles killing cranes in the southeastern United States (S. G. Hereford, pers. comm.), and general observations that eagles attack cranes on migration in the Mississippi Valley (R. P Urbanek, pers. comm.) and the Rio Grande Valley (R. C. Drewien, pers. comm.). Here, we provide data on Golden Eagle attacks on captive-reared cranes. Most of our observations are for attacks that occurred while our birds were in flight following motorized vehicles
And some interesting notes on cooperative hunting.
Some generalizations surface: over half (8 of 15) of the attacks were by two or more eagles. Of these, six involved two birds, probably adult pairs. The seventh included one adult and one juvenile; the eighth included two juveniles and one adult. The attacks generally came from high above and always from behind the cranes. As far as we could tell, all attacks were focused on the trailing crane(s). All three cranes captured during migration were trailing birds. All were grasped from behind and held as they plummeted earthward. Although the long duration and long distance of some flights performed by our trained juvenile cranes indicate that they were physically fit, our migrations were peculiar in that they were led at lower altitudes than normally seen for wild crane migrations. Our birds were thereby more vulnerable to eagles than wild cranes would have been. This was especially true when our birds were low to the ground while crossing mountain passes. The cranes suffered several attacks over passes, and two of the three cranes struck on migration were at mountain passes. However, some attacks occurred in open habitat far from either canyons or mountains.
Cooperative hunting by Golden Eagles is generally perceived as being less common than our data suggest. Nevertheless, about 37% (43 of 115) of capture attempts by Golden Eagles in an Idaho study were when hunting in tandem (Collopy 1983). Hunting by larger groups of Golden Eagles is probably chaotic or pseudocooperative (Ellis et al. 1993).
